1. Field of the Invention
This invention relates to a process cartridge and a developing apparatus mounted to an image forming apparatus of the electrophotographic type such as a copier, a page printer or a facsimile apparatus, and further to agitating means mounted to the process cartridge and the developing apparatus.
2. Related Background Art
An example of the developing apparatus is shown in FIG. 15 of the accompanying drawings.
This developing apparatus 105 is provided with a developer container 105a for effecting the storage and custody of a toner (developer) 106, and a developing roller 108 which is a developer bearing member. A developing blade 109, which is a developer regulating member, bears on the developing roller 108, and serves to regulate the amount of the toner 106 on the developing roller 108 and charge the toner 106.
Also, there are often provided agitating means 110 and 111 for loosening the toner 106 in the developer container 105a and feeding it to the developing roller 108 side. These agitating means 110 and 111 have the action of stabilizing the supply of the toner 106 to the developing roller 108 and creating the flow of the toner 106 in the directions of arrows P1 and P2 to thereby make the circulation of the toner great and moderate the deterioration of the toner 106.
By an engine controlling portion 107 provided with a power source for driving an image forming apparatus and a high voltage circuit for supplying a bias for effecting image formation, a developing bias, comprising an AC bias superimposed on a DC bias, is imparted between a photosensitive drum 101, which is an electrophotographic photosensitive member, and the developing roller 108, and the toner 106 is supplied from the developing apparatus 105 as described above, whereby a latent image, formed on the photosensitive drum 101, is developed.
Now, recently a resolution of 1200 dpi or 2400 dpi has been required and a high quality of image corresponding thereto has become necessary. As a means for achieving it, it has been found that a fine-grained toner is highly effective and preferable for bettering dot reproducibility. Further, it has been found that an average toner-grain diameter of 7 um or less leads to the capability of developing a latent image with high fidelity thereto.
Also, the coat amount of the toner in the developing area of the developing roller 108 is reduced, whereby the wasteful development by the toner can be suppressed and the scattering of the toner to the vicinity of the latent image can be decreased, and sharp characters and lines can be reproduced.
However, by the toner being fine-grained, the surface area per unit volume of toner becomes larger and therefore, the deterioration speed by the friction between toner grains becomes higher. Also, under a high-humidity environment, the humidity-absorbing amount of the toner tends to become greater, and the toner becomes liable to cohere.
Therefore, in a situation wherein the printing operation under a high-temperature, high-humidity environment is not being performed, the toner may sometimes absorb humidity and comes to cohere near the portion of contact between the developing roller 108 and the development blade 109. Thus, even when the printing operation is entered and the developing roller 108 is driven, the toner that has cohered does not immediately go to pieces. Therefore, the cost amount of the toner on the developing roller partly becomes small and the density sometimes becomes thin in the conveying direction. So, there has been desired agitating means that can obtain a sufficient agitating force even in a small space.
Also, by the coat amount of the toner on the developing roller 108 being reduced, the rate of the toner pushed aside by the developing blade 109 is increased and therefore, the deterioration by the friction or the like between toner grains becomes liable to be caused.
Further, in the above-described developing apparatus 5, it is difficult to utilize all of the toner 6 contained in the developer container 5a and accordingly, it is required that the toner be utilized without waste as far as possible.
It is a primary object of the present invention to provide an agitating member that can obtain a sufficient agitating force even in a small space.
It is another object of the present invention to provide agitating means and a developing apparatus that enable a toner contained in a developer container to be utilized without waste as far as possible.
It is another object of the present invention to provide a developing apparatus in which the deterioration of a toner can be prevented and even under a high-temperature, high-humidity environment, the scattering of the toner is small and a high quality of image can be obtained and further, uniform density can be obtained in an image area.
It is another object of the present invention to provide a process cartridge in which the deterioration of a toner can be prevented and even under a high-temperature, high-humidity environment, the scattering of the toner is small and a high quality of image can be obtained, and a stable density can be obtained during the service life of the cartridge, and to provide an electrophotographic image forming apparatus provided with such a process cartridge.
It is another object of the present invention to provide an agitating member for agitating a developer comprising:
a metal shaft;
a plate member joined to the metal shaft; and
a sheet member joined to the plate member, the sheet member being free to curve.
It is still another object of the present invention to provide a developing apparatus comprising:
a developer bearing member bearing a developer thereon;
a developer container containing the developer therein; and
an agitating member provided in the developer container for agitating the developer while supplying the developer to the developer bearing member, the agitating member including:
a metal shaft;
a plate member joined to the metal shaft; and
a sheet member joined to the plate member, the sheet member being free to curve.
It is yet still another object of the present invention to provide a developing apparatus comprising:
a developer bearing member bearing a developer thereon;
a developer container containing the developer therein, the developer being a monocomponent developer of which the weight average grain diameter is 7 xcexcm or less; and
an agitating member provided in the developer container for agitating the developer while supplying the developer to the developer bearing member, the agitating member including:
a straight metal shaft;
an L-shaped metallic plate member joined to the metal shaft, an end of the plate member being incapable of contacting an end of the developer container;
a sheet member joined to the plate member, the sheet member being free to curve, and an end of the sheet member being capable of contacting a bottom portion of the developer container;
another agitating member, the agitation loci of the agitating member and the another agitating member overlapping each other in a vertical direction, a diameter of the agitation locus of the another agitating member being larger than a diameter of the agitation locus of an agitating member, the agitation center of the another agitating member lying above an agitation center of the agitating member, the diameter of the agitation locus of the another agitating member being 30 mm to 50 mm, a peripheral speed of the another agitating member and a peripheral speed of the agitating member having differences relative to the developer bearing member, the peripheral speeds of the another agitating member and the agitating member differing from each other; and
a developer regulating member for regulating the developer borne on the developer bearing member, the amount of applied developer regulated by the developer regulating member being 1.5 mg/cm2 or less.
Other objects and features of the present invention will become more fully apparent from the following detailed description when read with reference to the accompanying drawings.